Scholars excluded from Japan's top science advisory panel said the move was unconstitutional and a dangerous sign of how newly installed Prime Minister Yoshihide Suga will wield power.
Suga broke precedent in rejecting membership to six scholars to the Science Council of Japan (SCJ), a body set up after World War Two to provide independent scientific input for policy-making.
The spurned academics had previously criticised government policy, including 2015 laws to allow Japanese troops to fight overseas.
Among the six were legal and constitutional scholars who said Suga's move was illegal and could prompt both parliamentary and criminal inquiries.
One of them, Ritsumeikan University law professor Takaaki Matsumiya told reporters on Friday that Suga was acting "similar to a dictator."
"He is reinterpreting Article 15 of the constitution in a way that he will be able to appoint or dismiss all public servants just as he likes," Matsumiya said. "This is a very dangerous direction that he is moving in."
Suga has said his decision had nothing to do with the scholars' positions on government-backed legislation, defending the decision as appropriate without disclosing reasons for their exclusion. Typically the SCJ's recommendations for membership have been approved by the serving prime minister.
Polls have shown that nearly half of respondents said they didn't find Suga's explanation convincing, helping to erode his support rating by seven points to 55% in the second survey since he took office last month following Shinzo Abe's resignation for health reasons.
Members of Suga's ruling Liberal Democratic Party met with former presidents of the SCJ on Thursday and voiced doubts about how the group recommends members and whether it should remain a state-affiliated body, the Jiji news agency reported on Thursday.
(Reporting by Rocky Swift in Tokyo)
